The present invention relates to the art of cored spring assemblies of the type formed from a continuously coiled spring wire and more particularly to an elongated spring assembly with a core captured in the center of the assembly for dampening electromagnetic energy.
The present invention is an improvement over the cored spring assembly disclosed in Meier U.S. Pat. No. 6,264,183. This prior patent includes not only a description of the type of cored spring assembly to which the present invention is directed, but also spring coiling machines for producing the assembly. This patent together with the various patents on spring coiling machines set forth in the introductory portion of that patent are incorporated by reference herein. The particular coiling machine for producing the present invention is well known and may be of the type that coils spring wire from the back of the machine, as shown in Meier U.S. Pat. No. 6,264,183, or from the side of the machine. Many coiling machines can be used to make the present invention. Meier U.S. Pat. No. 6,264,183 shows the prior art spring assembly, together with various coiling machines to make such assembly.
Also incorporated by reference herein is Green U.S. Pat. No. 3,882,341 disclosing a cored coiled spring assembly with reduced diameter end portions capturing the core in the center of the assembly. This cored spring assembly is essentially the same as the spring assembly shown in Meier U.S. Pat. No. 6,264,183 and is incorporated by reference herein as background.
The cored spring assemblies shown in Meier U.S. Pat. No. 6,264,183 and Green U.S. Pat. No. 3,882,341 are for use in an internal combustion ignition systems to dampen electromagnetic energy generated by the ignition system. The prior art spring assemblies include a ferrite or ferromagnetic core, inserts or plug held in the center of a single continuous coiled spring. The insert or core is maintained in place within the center of the assembly by merely reducing the diameter of the coiled spring being formed by the coiling machine at opposite ends of the center portion. The reduced diameter sections are intended to capture the core. This type of coiling operation makes the diameters of the reduced diameter portions on opposite sides of the core quite critical. If an undersized core is used, the reduced diameter portions can not assure that the core is captured and maintained in the center of the assembly. Furthermore, if the core wears on the reduced diameter portions, there is a possibility that the capturing of the core is compromised.
The present invention is directed to an elongated spring assembly with a core, as defined above, wherein the centered core is captured by lugs on opposite sides of the core. These lugs are formed from the wire used to coil the spring in the coiling machine. By interrupting the coiling of the spring wire and deforming a length of the wire to extend in a chordal direction across the central passage of the coiled wire a first lug is formed. Thereafter, the coiling machine coils a large diameter center portion to receive the core. At the end of the center portion surrounding the core, the coiling machine is again manipulated to bring a second length of wire across the passage at the end of the core. Then, the coiling operation continues to complete the assembly. In practice, the two end portions of the coil have a slightly smaller diameter than the center diameter that surrounds the core. The lugs at each end of the center portion are chordally disposed across the internal passage of the spring to positively capture the core within the center portion of the spring. Consequently, the coiling action first coils an end portion of the spring assembly. A length of wire is then drawn chordally across the passage of the spring. Thereafter, a larger diameter of the coil assembly is coiled by the coiling machine. This larger diameter receives the centered insert or core. Then the coiling machine hesitates and draws another length of wire chordally across the internal passage. The remaining end is coiled in accordance with normal practice. Consequently, the coil assembly has end portions with one diameter and a center portion with a large diameter. In practice, the core is cylindrical and has an outer diameter less than the internal diameter of the passage in both the end portions and the center portion. These diameters are specifications of the end user. As these specified diameters are greater than the core, the present invention has a distinct advantage. The chordally extending lugs are across the center passage of the spring assembly. This positively captures the core in the center of the assembly, even though the core could possibly slip through the end portions of the assembly. Reduced diameters do not positively block movement of the core.
In accordance with the present invention there is provided a spring assembly comprising an axially extending coil formed from a spring wire and having first and second ends and a length there between. The coil has a passage with a generally circular cross-section. The coil includes a first end portion with a first diameter and extending inwardly from the first end, a second end portion with a second diameter and extending inwardly from the second end, and a third center portion with a third diameter between the end portions. An elongated ferromagnetic core is positioned within the passage of the coil at the center portion and two spaced lugs are provided on opposite ends of the center portion. The lugs are formed from a short length of the same wire and join the center coiled portion with the end coiled portions. These lugs extend chordally across the cross-section of the center passage to capture the core in the center coiled portion.
In accordance with another aspect of the present invention, the two end portions have the same diameter, whereas the center portion has a larger diameter to facilitate the ferromagnetic core. The chordal lugs preferably extend diagonally across the center passage of the coiled spring assembly to positively capture the core in the center of the spring assembly.
In accordance with another aspect of the present invention there is provided a method of making a cored spring assembly. The method comprises coiling spring wire into a first diameter to define a central passage with a circular cross-section. Then, the coiler draws a length of the wire chordally across the passage to define a first lug. Thereafter, the coiling of the wire continues to form a second diameter center portion with a cavity or center passage. During formation of the center portion, or after the formation, the method includes inserting an elongated ferromagnetic core into the cavity. Thereafter, a second length of wire is drawn chordally across the passage to capture the core in the cavity. Forming of the second lug is followed by coiling the wire into a diameter generally equaling the first diameter to complete the spring assembly. This method is performed by standard spring coiler machine that is hesitated during the coiling operation to draw a length of wire, as a lug, across the center of the coil assembly to positively prevent the core from moving axially from the center of the spring assembly. Of course, xe2x80x9ccenterxe2x80x9d means intermediate and not actually at the midpoint of the assembly.
The primary object of the present invention is the provision of a cored coil spring assembly including lugs on opposite sides of the core to hold the core within the assembly.
Another object of the present invention is the provision of a cored spring assembly, as defined above, which spring assembly positively captures the core in the center portion of the spring assembly to prevent any possibility of axial displacement.
Still a further object of the present invention is the provision of a cored spring assembly, as defined above, which spring assembly can replace the spring assembly shown in Meier U.S. Pat. No. 6,264,183 with a more positive capturing of the centered core.
Still another object of the present invention is the provision of a method of making a cored coil assembly, which method merely coils the assembly and hesitates the coiling process at two spaced locations on opposite sides of the center portion to form lugs that capture the core in the assembly.
These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings.